The present invention relates to internal combustion engines and, particularly, to higher efficiency, clean gasoline engines adapted for use in automobiles, aircraft, boats, etc.
Internal combustion engines which burn air-gas mixtures are, of course, on common use and obviously require little description. Customarily, four-stroke engines are used, the strokes being the familiar intake, compression, power and exhaust. Combustion occurs near the end of the compression stroke. Specially-designed carburetors mix the fuel with the air. Ignition normally is accomplished by a spark. The power output of the engine is operator-controlled, usually be means of a throttling action or, in other words, a restriction of the flow of air to the engine. Power is taken off the reciprocating pistons by a crank shaft and the net power produced by the engine taken off the end of the crank shaft. Cooling normally is achieved by circulating water which requires the conventional water pumps, radiator, fan hose, etc. Gasoline obviously is the preferred fuel because of its large number of retail outlets, as well as the fact that it is reasonably safe compared with liquified gases and not as messy as diesel fuel.
However, engines in present use have some well-recognized limitations and disadvantages. For example, fuel economy or, in other words, the useful energy produced per unit mass of fuel, is poor both in an absolute and a relative sense. Only a small fraction of the energy in the gasoline fuel is converted into useful work and, in fact, diesel engines are much more efficient, although they do have other characteristics which have limited their popularity. Another ever-increasing problem is that the common gasoline engine produces excessive levels of pollutants consisting of unburned fuel and of various combustion products. Most of these deficiencies are the result of one or more characteristics of this type of engine. To a considerable extent, the deficiencies are due to inadequate control of the air-fuel mix, as well as the fact that power output is controlled by throttling. Further, due to detonation problems, there are definite limitations on compression ratios and hence, the efficiency of the engines.
As to the adequate control of the air-fuel mixture, it is known that a great deal of energy is wasted because a significant fraction of the gasoline does not burn during the combustion process. This unburnt fuel is exhausted and it contributes heavily to pollution. The problem is caused by poor ratio control by the carburetor and poor mixing of the air and the fuel in the carburetor, as well as the induction system and the cylinder. There also is inadequate control of the sizes of the fuel particles.
As to the throttling action conventionally employed in this type of engines, it is a fact that conventionally the displacement, maximum volumetric efficiency, rpm range, etc. of the engine, are determined by the peak power and torque required from the engine and that these peak values are obtained with the throttle open. Under all other operating conditions, the throttle is partially closed so that the engine must do a certain amount of `negative` work against the throttle on the intake stroke. The problem is particularly severe in the United States where engines of very large displacement and high peak power are common. Under normal operating conditions, the throttle must be nearly closed most of the time and more energy is wasted in the engine than is required to do useful work.
As to compression ratios, it is known that the efficiency or, in other words, the energy output per mass of fuel of these engines increases with increasing compression ratios. However, the maximum possible efficiency of an engine is seriously limited by the fact that at a compression ratio of about 12 to 1, the temperature of the air-fuel mixture can reach levels at which spontaneous combustion occurs. In other words, detonation occurs and such detonation can produce serious damage. The problem is that at high compression ratios, the air and fuel mixture is very hot, due to adiabatic compression occurring prior to ignition, and, of course, the burning of fuel increases both the temperature and the pressure to even higher levels. Chemical changes then occur in the unburnt part of the charge and these changes tend to make the last part of the charge prone to explode. Numerous efforts have been directed at obtaining maximum compression ratios without detonation. Such efforts usually involve making the bore of the engine smaller or using higher octane gasolines as well as additives such as tetraethyl lead to suppress the detonation. Water also has been used as a suppressor, although its use in the common or popular engines is not practiced.
The design of the combustion chamber and intake port also has received considerable attention, mostly directed at providing a correct amount of turbulence or swirl. Generally, ignition should occur near the center of the charge and burning should proceed in a fairly symmetric manner through the charge. With such symmetry, the time available for the chemical changes is reduced and the last bit if fuel and air to be burnt is at a distance from the spark gap and in the coolest part of the combustion chamber.
However, the common engine leaves a great detail to be desired with regard to controlling the burning process to a degree capable of eliminating detonation in high compression engines.
It is recognized that the design of internal combustion engines involves a very large number of factors, not the least of which involves cost and operating efficiency considerations. In fact, most any engine in popular use represents a compromise between power, weight, size, efficiency, and cleanliness. However, it is believed that existing compromises can be significantly improved and many of the details which will be described are directed at such improvements.
The invention is concerned with a number of features and objects which will be considered in detail in the ensuing description. Some of the more important objects include:
the provision of an improved combustion chamber to achieve better air-fuel mixing and to minimize the problem of undesirable detonation;
the use of finely-divided droplets in the incoming air stream to act as a detonation suppressor and also to cool engine parts;
the provision of an improved air supply for the engine to avoid the disadvantages inherent in conventional throttling;
the provision of an improved fuel injection system to meter increments of finely-divided fuel particles into the combustion chamber;
the provision of an improved control system for varying the metered amounts of both fuel and water, and improvements of the safety and performance of the high pressure fuel injection systems normally used in engines of this type.